1. Field of the Invention
The present invention relates to a semiconductor device having interconnections and a via-plug for connecting the interconnections together, and to a fabrication method for such a semiconductor device.
2. Description of the Related Art
Among semiconductor devices such as memory and logic devices are those that conventionally include an interconnection structure in which interconnections are connected together by via-plugs. FIG. 1 is a sectional view showing an example of the configuration of a semiconductor device of the prior art. As shown in FIG. 1, the semiconductor device is a configuration that includes: interconnection 120 on lower dielectric film 110 that is formed on a semiconductor substrate (not shown); via-plug 230 that is connected to interconnection 120; and interconnection 140 that is connected to via-plug 230. Via-plug 230 and interconnection 140 are formed as a single unit.
The effect of the shape of via-plugs upon stress migration in such an interconnection structure has previously been documented (T. Oshima et al., “Suppression of stress-induced voiding in copper interconnects,” IEDM (2002)).
However, although the effect of the shape of via-plugs upon stress migration has been touched upon in the above-described literature, nothing has been disclosed regarding methods of solving this problem, and it is unclear how stress migration can be reduced.